This invention relates to the forming of can ends for seam joining to can bodies. In the art of can making, can ends have been made over 100 years in substantially the same way, by cutting a blank and forming a can end and curling inward the peripheral portion for subsequent assembly to a can body in a seaming machine. The punching and forming of the can end are accomplished in one operation, and then a second operation is required to curl the peripheral portion of the can end inward.
The curling is not an expensive procedure, and many machines are available which perform the curling step. However, the curling step is one additional step which adds expenses and potential problems to can end making. Moreover, the curling for over 100 years has compressed the peripheral material of the can end inward, thus increasing thickness and raising the potential of wrinkling or otherwise deforming the inward curl, which may cause imperfections in the seam and result in a less than perfect seal.
In large can ends, such as used for example in pretzel tins or cookie tins, the curling machines are large and expensive, adding an additional problem which has existed in the prior art.
In the present invention can ends refers to all ends including closure ends. In the beverage industry, for example, there are 2-piece and 3-piece cans. A can body has either one or two can ends. One end usually has a pull tab.
A special problem exists which requires curling of the can ends.
Can ends and cans are formed in high speed equipment. It is necessary to stack can ends together and to be able to separate them quickly and without error when rapidly feeding them to automated down-stream equipment. If there are no curls, the ends would tend to stick together. The peripheral curls aid the separation of the can ends in rapid unstacking operations.
In making can ends, it is conventional to punch and form the can ends in one step, and then to chute the can ends to conventional curling machines to curl the ends and then to stack the ends for transfer to automated down-stream equipment.
The seaming panels have the same diameter increments on small diameter can ends as on large diameter can ends. In large can ends, the seaming area may be a small percentage of the total area of the ends. In small can ends, the seaming panel may be a large percentage of the total end area and material.
In the United States, about 100 billion beverage and beer cans are made out of aluminum annually. One company alone makes about 20 billion cans a year in the U.S., and about an additional billion worldwide.
It can be appreciated that a saving of a single step in the production of can ends for the beverage industry, even while saving only a small amount of money per can end, would be multiplied by a number of ten to the eleventh power through the entire beverage industry, and would amount to substantial savings.
If a savings of metal, for example 1%, could be realized in the manufacture of can ends for the beverage industry, that would be equivalent to the metal used in one billion can ends and would result in a substantial saving.
The saving of metal in can ends is the reason that can bodies are necked-in, which is a common practice, at the present time of this invention.
Long standing needs continue for reducing steps, tooling and machines required for the manufacture of can ends. Long standing needs exist for the reduction of metal used in the manufacture of can ends.